Diarrhoeal Diseases Flashcards
What are the consequences of sodium chloride and water loss due to diarrhoea?
Leads to dehydration and thus volume depletion. Leads to decreased GFR and tubular luminal flow rate. Reduced luminal flow rate allows increased tubular reabsorption of urea so serum urea rises. Creatinine rises too in significant fluid reduction but to a lesser extent.
What are the consequences of loss of potassium due to diarrhoea?
Can result in hypokalaemia. Only 2% of total body potassium is in the extracellular compartment but this is important as potassium ions in the plasma determine the resting membrane potential of cells, such as the muscle and nerve cells of the heart. Therefore, very high or low potassium levels can precipitate threatening cardiac arrhythmias such as ventricular fibrillation and asystole.
What are the consequences of a loss of bicarbonate?
Can result in a metabolic acidosis.
Why do you have to be careful when prescribing IV fluids to someone with cardiac disease?
Patients with left ventricular dysfunction are liable to develop pulmonary oedema if given too much IV fluid too quickly.
What 3 things do you need to take into account when calculating how much IV fluids to prescribe?
1) Measured losses (urine, vomit, diarrhoea, surgical drains etc.)
2) Insensibile losses (fluid loss via skin and respiratory tract, around 800ml daily in normal individuals. Much higher in burns patients).
3) Previous day’s deficit (PPD). This is claculated by subtracting the previous day’s fluid intake (oral and IV) from the sum of measured losses and insensible losses.
In what type of patient might insensible losses increase?
Burns patients, people on ventilation, pyrexia.
When is 5% dextrose used?
Used when there are no electrolyte losses. The dextrose component is metabolised in the body to carbon dioxide and water, hence this fluid is used when only water replacement is required.
When is 0.9% saline (physiological saline) used?
It is used when there is sodium and water depletion. This fluid contains 9g of sodium chloride (or 154mmol each of sodium and chloride) per litre. Therefore, it is most important extracellular ions in near physiological concentration.
What is the minimum daily potassium loss?
60 to 80mmol of potassium required per day.
What is a dangerous amount of potassium chloride supplementation to give?
20mmol of KCl per hour
40mmol of KCl per litre of fluid
140mmol of KCl per day
What cardiac complications can occur in a patient with hypokalaemia?
Atrial fibrillation, cardiac arrest, SVT and asystole.
What is a prebiotic?
A non digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity in one or a limited number of bacteria in the colon that can improve human health.
How many litres of fluid does the small intestine and colon absorb a day and where does it come from?
8 litres in total. 6 litres secreted into the lumen from salvia, gastric, pancreatic and bile secretion. 2 litres of dietary fluid.
What happens in mild diarrhoeal disease?
Reduction of absorption capacity is compensated for by increased colonic absorption.
What is the infectious dose, ID-50?
The dose of an organism required to infect 50% of the target population.
